Lower respiratory infections claimed 2.5 Million lives in a single year

Despite progress in reducing childhood mortality, why do lower respiratory infections continue to claim millions of lives? A comprehensive study examining global trends from 1990 to 2023 addresses this question by investigating the pathogens responsible for these infections, their impact across age groups, and disparities between countries.

The study, which included Assoc. Prof. Ömer Ataç, a faculty member at Istanbul Medipol University at the time of the article’s publication, was published in The Lancet Infectious Diseases under the title “Global burden of lower respiratory infections and aetiologies, 1990–2023: a systematic analysis for the Global Burden of Disease Study 2023.”

Alongside the progress achieved in reducing childhood mortality, the research highlighted persistently high numbers of deaths among older adults and substantial disparities between countries.

DATA FROM 204 COUNTRIES AND TERRITORIES ANALYZED
Conducted as part of the Global Burden of Disease Study 2023, the research estimated the incidence of lower respiratory infections, associated mortality, and their impact on healthy life expectancy across 204 countries and territories. The analysis evaluated 26 categories of causative pathogens, including bacteria, viruses, fungi, and parasites.

Lower respiratory infections were defined as physician-diagnosed pneumonia or bronchiolitis (inflammation of the small airways in the lungs). COVID-19, tuberculosis, and pertussis (whooping cough) were excluded from these estimates because they are assessed separately in the Global Burden of Disease Study.

The researchers integrated mortality records, hospital data, disease surveillance systems, and published studies using statistical models. This approach enabled them to examine not only the overall burden of mortality but also how it varied by age, sex, geographical location, and causative pathogen.

242 MILLION INFECTION EPISODES IN A SINGLE YEAR
According to the study’s estimates, approximately 242 million episodes of lower respiratory infections occurred worldwide in 2023. The total number of deaths attributable to these infections was estimated at approximately 2.5 million.

Between 1990 and 2023, both the mortality rate and the total number of deaths declined. The annual mortality rate fell from 55.7 to 31 deaths per 100,000 people, while the total number of deaths decreased from approximately 2.97 million to 2.5 million.

However, a separate analysis of the 2010–2023 period revealed a different pattern. Although the population-adjusted mortality rate declined, the total number of deaths did not decrease. Instead, deaths rose slightly from approximately 2.44 million in 2010 to 2.5 million in 2023.

MORTALITY RATE AMONG CHILDREN DECLINED BY ONE-THIRD
Among children under five, the annual mortality rate associated with lower respiratory infections decreased by 33.4% between 2010 and 2023. The total number of deaths also fell from approximately 936,000 to 610,000. Nevertheless, these infections accounted for 13.1% of all deaths among children under five in 2023.

The study also assessed the 2025 target established under the Global Action Plan for the Prevention and Control of Pneumonia and Diarrhoea. The approximate threshold used for this target was fewer than 60 deaths annually per 100,000 children under five. However, the global mortality rate in 2023 was estimated at 94.8 per 100,000.

Although 129 of the 204 countries and territories examined had mortality rates below this threshold, the global target had not yet been achieved.

HALF OF ALL DEATHS OCCURRED AMONG PEOPLE AGED 70 AND OLDER
Among the age groups examined, the highest mortality rate was observed in people aged 70 and older. In 2023, the annual mortality rate in this population was estimated at 231.6 deaths per 100,000 people.

The total number of deaths among people aged 70 and older increased from approximately 936,000 in 2010 to 1.25 million in 2023. Consequently, this age group accounted for half of all deaths worldwide. Although the population-adjusted mortality rate declined over the same period, the absolute number of deaths increased.

The researchers noted that age-related changes in the immune system, frailty, and the coexistence of multiple medical conditions contribute to more severe outcomes from these infections. They emphasized the need to strengthen early diagnosis, timely treatment, and adult vaccination programs.

GEOGRAPHICAL DISPARITIES SIGNIFICANTLY INFLUENCE MORTALITY
The impact of lower respiratory infections varies considerably across the world. The study found that the highest mortality rates were concentrated in countries in sub-Saharan Africa. When broader geographical regions were compared, sub-Saharan Africa was also the region furthest from achieving the global mortality target for children under five.

The study examined these disparities in relation to factors such as income, access to healthcare services, and exposure to environmental pollution. The researchers emphasized the importance of expanding vaccination coverage and improving access to healthcare in regions with a high disease burden.

The findings demonstrate that improvements in global averages alone are insufficient. Strengthening access to preventive interventions, diagnosis, and treatment in countries experiencing the greatest losses remains essential to achieving the goal of reducing childhood mortality.

ONE BACTERIUM ACCOUNTED FOR APPROXIMATELY ONE IN FOUR DEATHS
The research also estimated the relative contributions of pathogens responsible for lower respiratory infections. Pneumococcus (Streptococcus pneumoniae), a bacterium that can cause pneumonia, ranked first among the causative pathogens, accounting for approximately 634,000 deaths. Nearly one in four deaths associated with lower respiratory infections was attributed to this bacterium.

Pneumococcus also ranked first in terms of incidence, accounting for approximately 58.3 million infection episodes. Influenza viruses ranked second, with approximately 22.5 million episodes of lower respiratory infections.

These findings highlight the importance of moving beyond the classification of lower respiratory infections as a single disease category and distinguishing the specific pathogens responsible for the greatest burden of illness and mortality.

VACCINATION AND EARLY DIAGNOSIS EMPHASIZED AS KEY PREVENTIVE MEASUREST
he researchers emphasized that vaccination, early diagnosis, and timely treatment must be addressed together to sustain the progress achieved in reducing childhood mortality and to prevent deaths among older adults.

The study highlighted the role of pneumococcal and Haemophilus influenzae type b (Hib) vaccines in reducing childhood deaths. Hib is a bacterium capable of causing serious infections in children. Vaccines and monoclonal antibodies developed against respiratory syncytial virus (RSV) were also evaluated. Monoclonal antibody interventions provide preformed protective antibodies against the virus.

The researchers identified equitable access to preventive interventions, stronger adult vaccination programs, efforts to address vaccine hesitancy, and more comprehensive surveillance of infectious pathogens as key priorities.

GLOBAL BURDEN OF 11 PATHOGEN CATEGORIES ESTIMATED FOR THE FIRST TIME
For the first time, the study provided comprehensive global and country-level estimates of disease incidence and mortality for 11 pathogen categories. Compared with the previous analysis, the number of microorganism samples used increased from 6.1 million to 12.7 million. Data from 20 countries that had not been represented in the earlier analysis were also incorporated.

The researchers acknowledged limitations arising from data gaps and methodological choices in statistical modeling. Nevertheless, the expanded analysis enabled a more detailed assessment of the causes of lower respiratory infections and provided an estimate of global progress as of 2023 toward the target of reducing childhood mortality.